TPND, hi...
Truly, do your best to relax because anxiety will only make it worse.
Acid reflux can cause esophageal spasms that mimic heart problems. It can be referred pain for anywhere in your body...and I don't say that to scare you.
Your physician seems to be on top of things, please try and trust her--although if things get worse or don't settle down, call her asap or go to the ER.
If she advised you to take any meds, including aspirin, please make sure you do...and if she didn't then please don't take anything as they can effect test results.

The scan sounds like the one I just had...they inject a small radioactive substance then time at different intervals to take "pictures" of your heart in action.
You lay on a table, have a pillow if you want one...they do their best to make you comfortable. The machine itself revolves around the top part of your body. It looks rather like a round disk.
You are not enclosed like you would be with an MRI.

It's very good for picking up even small nuances in the heart function.
I wish you well with it...that you get answers and any treatment necessary.

It's hard, I know, not to freak out about it. Do whatever you can to remain calm/relaxed...
Please again. If anything worsens, either call your physician or go to the ER. Better safe than sorry.
One thing they did for me at the ER was to give me a cocktail of drugs to see if it was related to acid indigestion by relieving my symptoms...it didn't so they proceeded with other testing.

Let us know how it goes, ok? you will be in my thoughts
Catherine